C-H Group as proton donor by formation of a weak hydrogen bond

Bonchev, Danail; Cremaschi, Pietro

doi:10.1007/bf02394559

Cited by 39 publications

(9 citation statements)

References 21 publications

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“…While the underlying cause of these frequency shifts is yet to be fully explored, they are ascribed here as arising from inductive effects. It is well established that alkyl groups are electron donating via the inductive effect, − and it is this electron donation from the adjacent methyl groups to the head group nitrogen that shifts their C–H stretching modes to higher frequencies relative to those of the methyl along the alkyl tail. − Furthermore, in sp 3 -hybridized quaternary ammonium cations (such as the nitrogen of the CTAB head group), the positive charge is distributed among the methyl hydrogen atoms. ,− This creates the potential for what is referred to as an “improper” hydrogen bond that forms between the methyl hydrogen and an electron lone pair on water (CH···O H-bond). ,,− ,− Interestingly, for such sp 3 -hybridized central atoms, this sort of improper hydrogen bond yields a bond contraction, causing the C–H modes to shift to even higher frequencies. ,,,,,,, A full discussion of the solvation environment of CTAB is complex − and beyond the scope of this work. Instead, an overview description of what has been found in these previous studies is given in the Supporting Information.…”

Section: Results and Discussionmentioning

confidence: 99%

Takes Two to Tango: Choreography of the Coadsorption of CTAB and Hexanol at the Oil–Water Interface

et al. 2019

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Mixed surfactant systems at the oil–water interface play a vital role in applications ranging widely from drug delivery to oil-spill remediation. Synergistic mixtures are superior emulsifiers and more effective at modifying surface tension than either component alone. Mixtures of surfactants with dissimilar polar head groups are of particular interest because of the additional degree of control they offer. The interplay of hydrophobic and electrostatic effects in these systems is not well understood, in part because of the difficulty in examining their behavior at the buried oil–water interface where they reside. Here, surface-specific vibrational sum frequency spectroscopy is utilized in combination with surface tensiometry and computational methods to probe the cooperative molecular interactions between a cationic surfactant cetyltrimethylammonium bromide (CTAB) and a nonionic alcohol (1-hexanol) that induce the two initially reluctant surfactants to coadsorb synergistically at the interface. A careful deuteration study of CTAB reveals that hexanol cooperates with CTAB such that both molecules preferentially orient at the interface for sufficiently large enough concentrations of hexanol. This work’s methodology is unique and serves as a guide for future explorations of macroscopic properties in these complex systems. Results from this work also provide valuable insights into how interfacial ordering impacts surface tensiometry measurements for nonionic surfactants.

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Section: Results and Discussionmentioning

confidence: 99%

Takes Two to Tango: Choreography of the Coadsorption of CTAB and Hexanol at the Oil–Water Interface

et al. 2019

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“…The existence of specific C-H... O interactions has been indicated in structural (e.g., Mathew & Palenik, 1974;Bernstein, Cohen & Leiserowitz, 1974) as well as in theoretical (e.g., Bonchev & Cremaschi, 1974) studies. It has been shown in the previous paper of this series that similar interactions between methyl groups and ether-oxygen atoms are strong enough to stabilize host-guest complexation in the solid state.…”

Section: C(10)-h(10) O(7)--c(8)mentioning

confidence: 99%

“…The H...O distances (2.38 and 2.45 A, values based on the experimental but underestimated C-H bond lengths) are slightly shorter than the sum of the corresponding van der Waals radii; they are, however, longer than the H... O distances in the intra-complex N-H...O hydrogen bonds. If we assume that the energy of a weak C-H... O interaction is of the order of 0.6-1.0 kcal mole -1 (Bonchev & Cremaschi, 1974) the cooperative effect of such interactions may add a significant contribution to other forces in determining the packing arrangement even in room temperature structures. Since the generally accepted operational definition states that hydrogen bonding exists if the …”

Section: C(10)-h(10) O(7)--c(8)mentioning

confidence: 99%

Structure and binding in molecular complexes of cyclic polyethers. II. Hydrogen bonding and ion pairing in a complex of a macrocyclic polydentate ligand with butylamine at 120 K

Goldberg¹

1975

Acta Crystallogr Sect B

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The crystal structure of a 1:1 complex of a macrocyclic polydentate ligand (3,6,9,12,15-pentaoxa-21-carboxybicyclo[15,3,1]heneicosa-1(21), 17,19-triene; Ct7H2407) with t-butylamine has been determined from three-dimensional intensity data collected on a four-circle diffractometer at 120 K. The crystal is orthorhombic, space group Pnrna. There are four molecular units in the unit cell of dimensions a= 17.811 (3), b= 13"920 (2) and c--8.763 (2)/~. The structure was solved by direct methods and refined by the least-squares procedure to a final R value 0.038 for 1791 observations above threshold. The ionic constituents of the complex are located on mirror planes. The large host and the smaller guest species are held together by N-H...O hydrogen-bonding and ion-pairing interactions, which also have an effect on the flexible molecular conformation of the substituted polyether moiety. The observed packing arrangement appears to be stabilized by a three-dimensional network of C-H...O interactions. The host-guest complex is characterized by a high degree of symmetry.

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“…It is for this reason that the decade of the 1970s saw a number of considerations of CHÁ Á ÁX bonds that were carried out for very small systems, with little biological relevance [108][109][110][111]. Moreover, these systems were considered by rather crude methods, either semiempirical, or ab initio but with small basis sets, and with no inclusion of electron correlation [112][113][114].…”

Section: Theoretical Answersmentioning

confidence: 99%

Contribution of CH· · ·X Hydrogen Bonds to Biomolecular Structure

Scheiner

Hydrogen Bonding—New Insights

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The history of weak CHÁ Á ÁX hydrogen bonds is discussed, beginning with early hints of their existence, to our current understanding of their widespread occurrence. While the presence of such bonds is no longer contested, there is a great deal of uncertainty regarding whether, and to what degree, these weak interactions may contribute to the structure of biomolecules. The ability of quantum calculations to address this issue, and their success to date, are discussed in detail.

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C-H Group as proton donor by formation of a weak hydrogen bond

Cited by 39 publications

References 21 publications

Takes Two to Tango: Choreography of the Coadsorption of CTAB and Hexanol at the Oil–Water Interface

Takes Two to Tango: Choreography of the Coadsorption of CTAB and Hexanol at the Oil–Water Interface

Structure and binding in molecular complexes of cyclic polyethers. II. Hydrogen bonding and ion pairing in a complex of a macrocyclic polydentate ligand with butylamine at 120 K

Contribution of CH· · ·X Hydrogen Bonds to Biomolecular Structure

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